1. Field of the Invention
The present invention relates to a detector for detecting a physical quantity from a value of an electric signal converted from the physical quantity, and, more particularly, to a detector having a self-calibration function and a characteristic corrective function.
2. Related Art Statement
Hitherto, a conventional detector has been, as disclosed in, for example, Japanese Patent Unexamined Publication No. 61-31952, arranged in such a manner that the measuring operation is stopped so as to start a calibrating operation which is performed as an offline operation. Furthermore, there has been disclosed, in Japanese Patent Unexamined Publication No. 61-212753, an apparatus capable of diagnosing deterioration by analyzing the characteristic observed in the detector. However, the apparatus of this type also performs, as an offline operation, the operation for diagnosing the deterioration.
The conventional calibration has been realized for the purpose of automating the offline operation. Furthermore, there has been a proposal that the reliability of a detector is improved by observing the line and giving an alarm if necessary as an online operation. However, since no measure has been taken for performing the calibration as an online operation, a problem takes place that the measurement is stopped for a relatively long time in comparison with the time in which the value of the measurement can be changed.